This invention relates to microelectronic circuit substrates of high integrity. Generally, these devices are produced by repetition of a number of processes such as formation of an insulating film on the surface of a semiconductor wafer, followed by etching of the film. For example, in the case of an insulating film formed on a silicon wafer, the etching includes a photolithographic process for forming a minute photo-resist pattern on the insulating film, followed by a wet etching process or a dry etching of the film, where the photo-resist pattern serves as a mask.
It is not uncommon for the photo-resist pattern formed by the photolithography to be insufficient of resistance to heat, or for it to deform if subjected directly to plasma, both of which may result in difficulty in achieving a proper minute etching.
In preparing thin films on for example silicon wafers for use in microelectronic circuitry, one possible technique for application of the thin film is via colloidal suspensions, i.e. sol-gels. This is a preferred method of deposit since there is no need for complicated, costly equipment and since the deposition rates and the stoichiometries can often be difficult to control in alternative methods of film production. A wide variety of materials can be produced by the sol-gel process, including oxides of titanium, vanadium, chromium, iron, cobalt, nickel, germanium, yttrium, zirconium, niobium, indium, tin, tantalum, lead, and even some rare earth elements. Thus, sol-gel derived crystalline films are very attractive to the electronics industry for use as conformal, insulating, or encapsulating layers in circuitry.
However, while several of the metal oxides are of interest as coatings, it would be advantageous to be able to use many of these materials as more than just conformal or encapsulating layers in electronic circuitry. However, in order to incorporate films into electronic devices, the films must be patterned.
In the past it has been known that gel films are not as hard and resistant to etching as the corresponding ceramic films. It would therefore be of a significant advantage, particularly in microelectronics, if sol-gel derived films could be patterned prior to the calcination of the gel to the polycrystalline ceramic.
It is therefore a primary objective of the present invention to devise a method where sol-gel deposited films can be patterned in a cost effective manner such that the film can be effectively used in microelectronic circuitry.
Another objective of the present invention is to provide a method of sol-gel film deposit patterning of metal oxide films in such a manner that the film's integrity is preserved without breaks, pinholes, etc.
Another objective of the present invention is to provide a sol-gel film deposited on a silicon wafer which is patterned, which has good integrity, and which can be densified and used in electronic devices.
The method and manner of accomplishing each of the above objectives will become apparent from the detailed description of the invention which follows hereinafter.